import java.util.*;

public class Test {


    public static void main6(String[] args) {
        char[] ch = new char[]{'a', 'b', 'c'};
        String s1 = new String(ch); // s1对象并不在常量池中
        s1.intern(); // s1.intern()；调用之后，会将s1对象的引用放入到常量池中
        String s2 = "abc"; // "abc" 在常量池中存在了，s2创建时直接用常量池中"abc"的引用
        System.out.println(s1 == s2);
    }

    public static void main(String[] args) {
        String s1 = "hello";
        String s2 = "hello";
        System.out.println(s1 == s2); // true

        String s3 = new String("hello");

        System.out.println(s1 == s3); // false

        String s4 = new String("hello");

        System.out.println(s3 == s4); // false

        System.out.println(s1 == s3); // false

    }

    public List<String> topKFrequent(String[] words, int k) {


        //1、统计每个单词出现的次数
        Map<String, Integer> map = new HashMap<>();
        for (String word : words) {
            if (map.get(word) == null) {
                map.put(word, 1);
            } else {
                int val = map.get(word);
                map.put(word, val + 1);
            }
        }


        //2、建立小根堆,指定比较的方式
        PriorityQueue<Map.Entry<String, Integer>> minHeap = new PriorityQueue<>
                (new Comparator<Map.Entry<String, Integer>>() {
                    @Override
                    public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {

                        if (o1.getValue().compareTo(o2.getValue()) == 0) {
                            //按照字母顺序建立大根堆
                            return o2.getKey().compareTo(o1.getKey());
                        }

                        return o1.getValue() - o2.getValue();
                    }
                });

        //3、遍历map 调整优先级队列

        for (Map.Entry<String, Integer> entry : map.entrySet()) {
            if (minHeap.size() < k) {
                minHeap.offer(entry);
            } else {
                Map.Entry<String, Integer> top = minHeap.peek();
                //如果当前频率相同
                if (top.getValue().compareTo(entry.getValue()) == 0) {
                    // 字母顺序小的进来
                    if (top.getKey().compareTo(entry.getKey()) > 0) {
                        //出队
                        minHeap.poll();
                        minHeap.offer(entry);
                    }
                } else {
                    if (top.getValue().compareTo(entry.getValue()) < 0) {
                        minHeap.poll();
                        minHeap.offer(entry);
                    }
                }
            }
        }

        List<String> ret = new ArrayList<>();
        for (int i = 0; i < k; i++) {
            Map.Entry<String, Integer> top = minHeap.poll();
            ret.add(top.getKey());
        }

        Collections.reverse(ret);

        return ret;

    }
}